feat(#1): implement user registration

[kukuruzvelt]

Description

As a user, I want to be able to register in the VilnaCRM.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [x] I have performed a self-review of my code.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING.md document.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.
• [x] You have only one commit (if not, squash them into one commit).

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #5 +/- ## ======================================== Coverage ? 100.00% Complexity ? 501 ======================================== Files ? 141 Lines ? 2245 Branches ? 0 ======================================== Hits ? 2245 Misses ? 0 Partials ? 0 ```

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[Kravalg]

It will be better to be consistent with the directory structure. There are a few methods to achieve a clean and understandable directory structure: functional/feature-based way or programming patterns/entities-based way

I think that we can use programming patterns-based way for naming the directories. We can achieve this using the deptrac